The Vitamin D Dilemma

Published on July 18, 2006

Vitamin D is important for immune system health, and we get it from the sun. That's why some scientists argue that protecting yourself from UV rays is detrimental to your health. Most dermatologists, however, disagree. We take a look at both sides.

vitamins In the past few years, controversy has raged among physicians and scientists about whether sun exposure is a beneficial source of vitamin D. Some assert that certain Americans suffer from vitamin D deficiency, and that vitamin D produced in the body by solar ultraviolet (UV) exposure may help prevent prostate, colon, breast, and other cancers, as well as bone diseases.

People are at greater risk for these diseases, they say, because dermatologists have scared them out of the sun. Since skin manufactures vitamin D in response to ultraviolet (UV) light, they explain, the simple solution to the deficiency is 5-10 minutes of unprotected UV exposure from the sun or tanning machines two or three times a week.

Most dermatologists and cancer groups, including The Skin Cancer Foundation, have argued strongly against this "solution," since all unprotected UV exposure contributes to cumulative skin damage, accelerating aging and increasing our lifetime risk of skin cancer. And a new analysis from the Department of Dermatology, Boston University School of Medicine, supports this stance.

The authors, Deon Wolpowitz, MD, PhD, and Barbara A. Gilchrest, MD, reviewed massive research on vitamin D and sun exposure. They found that in regions where people have greater sun exposure, fewer cases of colon cancer occur (presumably because of sun-induced vitamin D), and fewer deaths occur from colon, breast, and prostate cancers. However, they pointed out that UV is an officially recognized environmental carcinogen. There has been "a near epidemic" of skin cancers, they say, with more than 1.3 million diagnosed yearly in the U.S.- and the cause of most is sun exposure.

As for the advocates of unprotected sun exposure, Drs. Wolpowitz and Gilchrest say the studies supporting them are of "variable quality" and merely "observational": The data generally link mortality from colon, breast, and prostate cancer in specific regions with the amounts of UV in those regions. Such studies may be confounded by climatic factors such as pollution, variations in population genetics (such as darker- or lighter-skinned populations), and cultural or lifestyle factors (such as socioeconomic status and diet). The studies cannot directly correlate disease with individual sun exposure, and "cannot establish that solar exposure decreases incidence or mortality from these cancers."

In contrast, research ranging from animal studies and surveys to large population studies and human DNA studies has strongly established the connection between sun exposure and skin cancer. Sun exposure also causes wrinkles, brown spots, leathering and sagging. Drs. Wolpowitz and Gilchrest further note that very small amounts of sun exposure provide all the vitamin D the body can manufacture. Even when you wear sunscreen, some UV reaches the skin, and this may be plenty, at least for fair-skinned individuals. "Greater exposure adds nothing to vitamin D stores, while increasing DNA damage in a linear fashion," they add. The authors conclude, "The tradeoff of vitamin D production today for photoaging and skin cancer decades hence may have made sense millennia ago, when life expectancy was 40 years or less, but it's a poor exchange when life expectancy has doubled, skin rejuvenation is a $35 billion/year industry, and one in three Caucasians develops skin cancer."

Fortunately, Drs. Wolpowitz and Gilchrest point out, there are "effective and almost effortless" noncarcinogenic alternatives-vitamin D-fortified foods and/or dietary supplements. James Spencer, MD, clinical professor of dermatology, Mount Sinai School of Medicine, New York City, concurs. If you want more vitamin D, he says, you can obtain all you need from your diet. "Drink vitamin D-fortified orange juice or milk or other enriched products. Eat salmon and other fatty fish. Or take a daily multivitamin containing 600 units of vitamin D. It's so easy. And it's a lot safer than lying in the sun or climbing undressed into a tanning booth and frying your whole body."

The Skin Cancer Foundation supports The Institute of Medicine of the National Academies’ Recommended Dietary Allowance (RDA) for vitamin D, which is 600 IU (International Units) a day for people between the ages of 1 and 70, and 800 IU a day for people ages 70 and older. For children under 1 year, adequate intake (AI) is 400 IU a day.